Indicator adjustment for sextants



April 6, 1948. c. o. ROTHWEILER 2,439,102

- INDICATOR ADJUSTMENT FOR SEXTANTS Filed June 12', 1944 s Sheets-Sheet 11 INVENTOR.

AT'TORNEK Aprll 6, 1948. c. o. ROTHWEILER INDICATOR ADJUSTMENT FOR SEXTANTS Filed June 12, 1944 w 3 Sheets-Sheet 2 AT TORNE April 1948. c. O..ROTHWEILER 2,439,102

INDICATOR ADJUSTMENT FOR SEX'I'ANTS Filed June 12, 1944 3 Sheets-Sheet 3 minimum \u nu INVENTOR. cmmzfia/y'amw ms ATTORNEY.

Patented Apr. 6, 1948 ,:iuNnIcA roRnmUsrMEnrtnonisnxtmms Charles W). RothweilerfMilwa-dkee, Wis. .AppficationJune 12, 1944, Serial No. 539,843

.My invention relates to improvements in "sex- "tan'ts and more ,parftierilafly to the type (if "sextant that "is employedffo'r measuring angular distances or dbseriiing altitude at ,sea'to ascertain latitude and longitude.

,I'Ihe object of m invention isltohrorfiide a se- I'v'iee 'offthe charaeter described that permits veriii cal andfhorizontail adjustmentdf the mountingto'f .theiindexerm "intheesserfihlyhf the devlce.

Another object 'off. .1ny, invention'is to provide a means of adjusting the index ,yoke tinnparallel relationto'the micrometer index drum.

A furtherobject of my inventionisito provide an enclosed resilient means adjustably mounted .into'th'e fframe supporting the worm, mounted on 'a;shai'ft journaled bearings, which shaft sup- :ports "therrnierometer" index drum.

A still further ohjec't of my invention is 'toc'onstruct the are ,of the sextant so as "to enable an insert provided withthe threadf'f or engagemerit withithe worm, to bez'sep'arateiy mounted totheradius of the aro segmerft.

Other "and further objeotsof "my invention will ioecomemore apparent as the description proceedswhen taken in conjunction with the d-rawingsin which e Figure l is -a. qilan view of the "front of "a sextant,

Figure 2 is a plan viewof therear -of-a sextant,

Figure 3 is an end *view of a sextant when tamin'g thetflescope,

Eigure '4 is a across-sectional wi'ew :of itheibearing supporting the :irxdexmarm Ito the are :se'g

Figure 7 is, a crosssecition of thenarcwand arc insert together with thetwermmassemhly,

figure 8 Lis s, cross-section of the hearing .on the worm (frame taken at the .Jine' 8+3 inwFigsslidablmmounted ontda sleeve :supported oy the to 3 shows the-,arcwsegment or frame of the device.

Therepis an-index arm -lrl ,pi-votally mounted at l2 to theatre segment I10. The index arm ll is provided with a rectangular aperture l3 throughtwhichthe characters :14 representing '"m the degrees of angle inscribed on the are seg ,ment ate-madewisible. Antindicating point 15 is shown inscribed ion the tacemfthe index arm -14 5a, t\the lower edge ofthe aperture 1 3.

The radial surf aeesof the are segment H1 is *mmrovided with an insert 16, having teeth I! -integral-therewith. Ihese teeth L! engage the thread-s atapered over-11118; which is mounted one-shaft 1.9, journaled in a, front bearing 1% and a rear bearing zi. .The bearings are an m integral sport-of a frame 22 which .is pivotally mounted to the vr seanward sideof the index arm H at 23, :rand -'a. ilever :M ,pivotally mounted to the index am, It at 25 has a.-=projecting memfoer en-ga,gin g a ,slot 26 in the frame 22, and

-g5-when-th1e =1ever 24'has pressure exerted thereonthe frame 2'2 is caused to move downward .thereby-disengagingthe worm 48 from theteeth H @onwth'e insert 46,; which fastened to the radial sur ftaee of-g-thegarersegment H1. A lever 72-4" is '30 permanently f-asterred to the index are as shown and :aots as, a means torsupport when thedever 2-4isactedupon.

Mounted withingthe;abearing 121 .is a, spring mem ber 2.1 as shown in-Ei-gure :3. l The bearing 2| wis provided at sits nlower .side withea. eavity 28 into which ithe spning fl l =i-s ,placed. There is :a rstop memben Z8 iastened by means of a. screw 30 thrnugh the-indexarm M as shown. This stop member 228 :pmjeots upward into the ,cavity 28 of th rhearing :21. adjustment .screw '31 engages a threaded pontion of-thecavity 2 8 and thereby permit-s adjustment of the tension of the swins i I ihe shatt IS being joumaIed in bearings zfl and -l-l xsupportsmthe wonm-tfl. However the bearing @24- is ,provided with iahsieeve 32 through which the shaft I9 passes. This sleeve 32 is *longer than the width of tithe hearing 21, and extends=outward therefrom togpermit the mount- :ing ran :indexwoke: 3:3, which Eyoke :is split at 34 and threaded to receive a clamping screw 35 as shown in Figure 9. The arrangement as described allows the index yoke 33 to be slidably adjusted onto the sleeve 32, either in horizontal alignment or in radial alignment therewith.

Inasmuch as the index yoke 33 carried an index arrow as shown at 36, the mounting of the index yoke pemnits this arrow to be adjusted to register with the readings on the micrometer index drum 31 fastened to the end of the shaft I9 and which when revolved will turn the shaft l9 and cause the worm l8 fastened thereto to revolve, forcing the index arm II in a radial path along the arc segment In due to the engagementof'theworm l8 with the teeth I! on of the index arm I I by means of a screw 39 being fastened to the index are H and engaging a slot 4!] in the frame 22. There is a washer 4| under the head of the screw 33 above the slot 46 in the frame. The assembly of the inserts it to the radial face .of the arc segment ii] is shown in detail in Figure '7. The fastening of the insert L IS to the" arc segment I!) is accomplished by means of the several screws 42 as shown.

In Figure 4 is shown in cross section the adjustable mounting of the index arm ll to the arc segment Hi. It will be noted-that the center 'i member 43, acts as a pivot point I2 and is fastened to the index arm by means of screws 44. The member 43 has an inwardly projecting arm 45 engaging the shell center 46 which shell 40 7 center is supported by means of its flanged face 41' contacting and resting upon the adjustment screws 48 in and through the arc segment ill. The center member 43 is held suspended within the shell center 46 by means of a slotted screw 49 and the entire shell and \center member arei the person who assembles the complete unit to 5 get accurate adjustment in any direction without having to make any mechanical changes on the parts themselves and to retain position of the parts Hland H by means of the screws 48.

is being used, and rest pins 63 being of the same length as the cover 5!! permit resting the device on its side without any other part of the device contacting the table or the like on which the device might be rested.

It is manifest to anyone familiar with the art that a precision instrument such as a sextant must necessarily be assembled in a manner that is so exact in every detail that the instrument will function correctly for the purpose for which it is intended. The arrangement as outlined in this description provides means for properly assembling the index arm to the arc segment by means of the screws 48. It will also be noted that the index yoke is slidably' mounted to the sleeve 32 and is held in correct position thereto by means of the clamping screw 35. Also the spring 31 in the cavity of the bearing 2| is mounted in a manner that entirely encloses this spring yet is adjustable for tension by means of the screws 3|. Attention is also respectfully called to the insert l6 which engages the entire radius of the arc segment l0 and the manner in which it is attached thereto permits removal and replacement to take care of any wear on the threads I! which engage the worm l8.

In the chosen embodiments of myinvention there are many improvements and featuresnot heretofore revealed in the art. I have shown these features and the manner in which they may be applied. However, I do not wish to confine myself to their specific construction for i the practice of the art there are many changes that may be made and different methods may be .employed without departing from the spirit of the invention, or the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent in the United States is: p

1. A device of the character described for use in combination with a worm gear; said ,device comprising a shaft, a worm mounted on said shaft, said shaft journalled in bearingsslidably mounted, means for engaging and disengaging the worm with said gear rack, one of said bearings provided with an outwardly extending sleeve, a graduated micrometer drum mounted to one end of said shaft, an index yoke adjustably mounted to the outwardly extending sleeve at'a point between said bearing and said micrometer drum. r 7 I 2. A device of the character described for use in combination with a worm gear supported'by a mounting, said device comprising a shaft, a worm 5 mounted thereon, a bearing plate, apair ofbear- The device is provided as shown in Figures 1,

2 and 3 with the conventional type of index mirror as shown at 53, a horizon mirror 54 and a telescope 55, the telescope being adjustably mounted on the bracket 56 by means of the screw There are colored lenses 58 adjustably mounted on a shaft at 59. These lenses are placed in direct alignment with the index mirror 53, and similar lenses 60 also adjustably mounted on the shaft at 5!, '70

51 engaging a bracket 56' which forms an integral part of the arc segment Iii.

" permits a ready support forthe device while it ings mounted to said plate, said plate pivotally mounted to said gear mounting, said shaft journalled in said bearings, one of said bearings provided with an outwardly extending sleeve, a graduated micrometer drum mounted to onewend of said shaft, an index yoke, said yoke adjustably mounted to the outwardlyextending sleeve at a mounted adjacent to said mounting and pivotally' supported at one of its ends by said mounting, thereby permitting engagement or disengagement of said worm with said worm gear, one: of said bearings provided with outwardly extending sleeve, a micrometer drum attached to one end of said shaft, an adjustably mounted yoke attached t0 the outwardly extending end of said sleeve at a point between said drum and bearing, said micrometer drum provided with graduations on its outer periphery, said adjustable yoke provided with an indicating point for registering with the graduations on said yoke.

CHARLES O. ROTHWEILER. REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 785,894 Kretschmar Mar. 28, 1905 786,274

Duff 7 Apr. 4, 1905 Number Number 

